Hard Miss

I've just replaced the timing belt/water pump/cylinder head in my 2005 Aveo. All went well, thanks to this forum. It runs great with one minor exception. I drive about 25 miles (40km) to work every morning. At about 18 miles (29km) I hit a stop light. At that stop light while I'm idling with the car in drive and the brakes applied, I get several very hard misses. The car shutters and seems like it just might kill. It happens a couple times, I proceed through the green traffic light, and drive the remaining 7 miles (11km) to my office and stop in the parking lot. I try to recreate the problem by doing the same thing I would at a stop light and it has gone away. It just seems to be that first stop after cruising at 60mph (96kmh) for a bit. It is possible that there was a miss before the engine rebuild, but it seems sill to think this is not related. Any thoughts?

My other question was about changing the oil. During the timing belt change, I also installed a rebuilt head. I used engine assembly lube for the cam and other moving parts. When should I change the oil, so as to get that out of the system? Right away, or at a normal interval?

Thanks all!